Cons:

Phantasy Star Universe is one of the biggest disappointments in years. I say this as a long-time fan of Phantasy Star Online, which was the best Diablo clone ever set in space. Sega's made radical changes, even bringing in some common MMO elements, but few of these really work out for the better.
As with most Phantasy Star games, PSU has few immediately obvious connections to previous editions. This time we're introduced to the Gurhal star system, in which three planets (and one space station) are under attack by an unknown alien menace. Though it could've worked out fine if handled differently, PSU doesn't do much with this setting, making me nostalgic for PSO's infinitely more compelling and creepy Planet Ragol. In fact, many aspects of PSU feel generic and flavorless compared to their PSO counterparts.
Alone in the Universe
One of Sega's major focuses this time around was the single-player experience, which throws you into the space hoodie of young Ethan Waber as he enlists in the Guardians (a peacekeeping force) and fights to defend Gurhal from enemies without and within. This basic storyline might've worked in more capable hands, but it's told poorly through cheap cinematics and weak voice acting. It's pretty impossible to care.

In between the goofy anime drama, you'll get to beam down to a planetary hotspot and smack some monsters with Ethan's lightsaber. The action soon proves repetitive, and it becomes apparent how hard it is to really care about a Diablo-clone character that you've not created yourself.
It'll probably take 15 to 20-odd hours to slog through all of the single-player chapters, which has the side effect of unlocking Extra Mode. Extra Mode lets you create your own custom character for offline-only play, sans any story bits. This sounds cool at first, but it's even less entertaining than the story mode. The only thing to do is play the same basic missions over and over again until you're strong enough to grind the next one in a similar fashion. It's like a training simulation for obsessive compulsive disorder, not a game you'd actually play for enjoyment.
Which brings us to the online game.